Presentation Transcript

Slide 1:

Decimals and
Place Value

Slide 2:

The zero and the counting numbers (1,2,3,...) make up the set of whole numbers. But not every number is a whole number. Our decimal system lets us write numbers of all types and sizes, using a clever symbol called the decimal point.
As you move right from the decimal point, each place value is divided by 10.

Slide 3:

In our number system, digits can be placed to the left and right of a decimal point, to indicate numbers greater than one or less than one. The decimal point helps us to keep track of where the "ones" place is. It's placed just to the right of the ones place. As we move right from the decimal point, each number place is divided by 10. Tens Ones Hundreds Tenths Hundredths Thousandths 5 2 1 4 3 6 and

Slide 4:

Watch the 9's for place value.

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Beyond the set of whole numbers, there are numbers that are less than one, but, greater than zero; they are known as fractional parts. The name lends itself well, as these numbers are parts, or fractions, of one whole. The rectangle, or whole, above has
been divided into 10 equal parts, or tenths.

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The rectangle is 1 whole. If I place the rectangle with
10 equal parts over the whole
I can see how 10 tenths = 1 whole.

Slide 7:

The hundredths place
has 100
equal parts.

Slide 8:

The rectangle is 1 whole. If I place the rectangle with
100 equal parts over the whole
I can see how 100 hundredths = 1 whole.

Slide 9:

What would six tenths
look like?

Slide 10:

How many tenths are shaded in? 0.4

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= = ____________ ____________ 0.8 0.4

Slide 12:

What would thirty
hundredths look like?

Slide 13:

How many hundredths
are shaded in? 0.20

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= ____________ 0.30

Slide 15:

= ____________ 0.58

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Decimals are equivalent, or =
to decimals in other place values. one tenth = ten hundredths Use your decimal squares to find: one tenth = _____ thousandths 100

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three tenths = ______ hundredths thirty

Slide 18:

seven tenths = ______ hundredths seventy

Slide 19:

Whole Number Portion
The whole number portion of a decimal number are the digits to the left of the decimal place.
Example:
In the number 23.65, the whole number portion is 23.
In the number 0.024, the whole number portion is 0 – There is nothing there!

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Which number is the whole number? 51.05 51 3.17 3 0.97 0

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The whole number is to
the left of the decimal. 70.006

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Less Than A Whole Number Portion
The less than a whole number (or fractional parts) portion of a decimal number are the digits to the right of the decimal place.
Example:
In the number 23.65, the less than a whole number portion is 65.
In the number 0.024, the less than a whole number portion is 024.

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Which number is the less
than the whole number? 34.77 77 2.09 09 0.1 1

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The less than whole
number is to the right
of the decimal. 99.321

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Hint #1: Remember to read the decimal point as "and" -- notice in the two numbers below what a difference that makes! 0.548 500.048

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Hint #2: When writing a decimal number that is less than 1, a zero is normally used in the ones place: 0.526 not .526 A symbol for nothing--our zero--had to be invented. Zero "holds the place" for a particular value, when no other digit goes in that position. For example, the number “0.506" in words means no ones, 5 tenths, no hundredths and 6 thousandths. Without a symbol for nothing, our decimal number system wouldn't work.

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Writing Word Names
For Decimals Look to see if there is a number to the left of the decimal; if so write it out. If there is no number to the left of the decimal, skip to step.
Write an and for the decimal point.
Write out the number to the right of the decimal. Do not yet include the place value.
Determine the place value of the last digit to the right of the decimal. Write the place value.

Slide 33:

Here's a shortcut for dealing with decimals:
Instead of writing out .345 = 3/10 + 4/100 + 5/1000, then finding the common denominator, adding, and reducing, just think: 1. Ask yourself: What is
the number? 345 2. Ask yourself: What is
the place value? thousandths 3. Then place the 345
over the 1000. 345
1000

Slide 35:

Lets Practice 0.53 53
100 0.3 3
10 0.801 81
1000 0.60 60
100

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Ordering Decimals o o $3.50 $3.83 $3.45 $3.09 Write them in columns so the place values line up. Compare the digits in each column, starting at the left. Which pizza
is cheapest?

Slide 37:

Log Book How many hundredths are
in four tenths? Explain how
you know and draw an example.

Slide 38:

There are forty hundredths in four
tenths. I know this because
one tenth is equal to 10 hundredths.
So 10 + 10 + 10 + 10 = 0.40. If you lay them on top of
each other they are the same.